CONTROL OF CONTACT BETWEEN ROLLERS (support rollers) AND TIRES (kiln tires), THROUGH LEAD WIRE
9.3.3 Procedure, calculation method and results
The method to follow for the trial with wire lead is to introduce, as long as the kiln is in service, a wire lead of 2 - 3 mm, between the supporting roller and the kiln tire, therefore the wire is compressed, as illustrated in Figure number 9.1.
Figure 9.1
0.0787 to 0.1181 inch lead wire . 0.0787 to 0.1181 inch lead wire .
9.3.3.1 Practical method execution
Immediately after starting and the first set in service for a new or just aligned kiln, i.e as long as the alignment is correct, it is recommendable to perform a trials set for all the supports with wire lead.
These trials set will form the comparison basis for all the subsequent trials.
A complete set encompasses six crushed wires coming from each support, three of them for each kiln tire. The trial with these three wires is made in front to three generatrixes, marked in the kiln tube with a space of 120 degrees between each of the, such as illustrated in the Figure number 9.2.
Figure 9.2
When the three generatrixes are marked in the kiln tube, it is more convenient to leave the generatrix A in the diametral plane, crossing through the man entrances center, and the other generatrixes displaced at a distance of 120° from there. Observe the letters sequence regarding the rotation sense.
Introduce the wire lead between the support roller and the kiln tire just in the moment when one of the generatrixes crosses through the kiln tire.
Provide, carefully, the crushed wire with date, support number, specify if it is right or left tire (seen from the kiln operator) and also write the corresponding generatrix number.
Figure 9.3
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A
B
C
DATE :
SUPPORT (OR BASE) NUMBER : SIDE: RIGHT/ LEFT
GENERATOR : OUTLET END
FLATTENED LEAD
DATE :
SUPPORT (OR BASE) NUMBER : SIDE: RIGHT/ LEFT
GENERATOR : OUTLET END DATE :
SUPPORT (OR BASE) NUMBER : SIDE: RIGHT/ LEFT
GENERATOR : OUTLET END
FLATTENED LEAD
Place the tag on those wire lead end closest to the kiln exit end, see Figure number 9.3.
The result of wire lead trials can be preserved fixing it with adhesive tape to a carton piece, or simply limiting to transfer, carefully, the wire leads contour to a paper and maintain it as illustrated in Figure number 9.4.
With support on Figure 9.4, which we section in 10 equal parts, to be identified as variables t, from t1 to t5, which is the exit side and we identify them as tU and from t6 to t10, which is the entrance side identified as tJ, see Figure number 9.5, the only recommendation is that the marking must be correct.
Subsequently, with the obtained measures the results are introduced in Form 9.1.
The mean values for every wire lead half are calculated, and the result is written in Form 9.1.
t1+t2+t3+t4+t5 t6+t7+t8+t9+t10
Tu = 5 Tj = 5
Left pulley wheel Right pulley wheel
Figure 9.4
KILN Number _____
Support Number _____
Date: ________
Center line Rolling ring ( Rim ) Rolling ring width
A B C A B C
INLET
OUTLET
}
L
C
}
Center line Rolling ring ( Rim ) Rolling ring width
A B C A B C
INLET
OUTLET
}
L
C
L
C
}
Immediately proceed to calculate the values tu - tj for each generatrix and its mean term is calculated, which is the value utilized to make comparisons.
The mean term results of tu and tj are written on the upper part and in the lower left table, the next step is to make the addition and the average is again obtained for every tire (right and left), subsequently the tire difference is calculated and the average tL is obtained.
The value of tL found, is compared with the value tL of the supports rest, specially with the mean terms previously confirmed for the corresponding support.
9.3.4 Interpretation of results
9.3.4.1 Supporting washers intersection
The kiln tire intersection i.e. how correct is the kiln tire and the support roller orientation regarding the kiln spinning or rotation.
In order to make comparisons the mean term tu-tj is used, if the kiln shaft is rectilinear (without warping), and the different supporting faces are in good conditions, the three differences tu-tj , one for each generatrix result almost equal.
Both kiln tire for a same support must be always of opposed intersection, when the kiln tires are located at parallel positions.
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Rolling ring width
A too big intersection results in a very big surface pressure, in a material overload, and the wanted effect to retain the kiln in the axial sense through an uniform axial pressure of the kiln tire is not obtained.
9.3.4.2 Kiln tire position in the lateral sense
The mean values calculated in the upper part of Form 9.1 are transferred to the lower left part, and the mean crushed widths tH and tV are calculated.
The values tH and tV specify he mean surface pressure, the values are compared, and if the difference exceeds 10%, the tires must be adjusted in the lateral sense. Nevertheless, in the support close to the gearing set a 20 % difference can be admitted.
9.3.4.3 Load over individual supports
Finally the mean width tL of all the wire leads crushed by the kiln tire are calculated. The value tL
represents an expression of the kiln tire total pressure over the corresponding support.
The value tL found is compared against the value tL of the supports rest, specially with the mean terms previously confirmed for the corresponding support.
9.3.4.4 Kiln tire inclination
If the lead wire trials insinuate that the tire or roller intersection is normal, whereas an examination on the tire supports show that the tire presses the roller downwards, the cause will be that the tire support face is not parallel to the kiln shaft. The tire or roller inclination must be corrected, through wedges (or shims) under one of the supports.
Additionally with the lead wires trial detection of irregularities as the following can be made:
Bearing width Intersection
(Mean term)
mm mm
500 2.5
600 3.0
700 3.5
800 4.0
900 4.5
1000 5.0
If the kiln tube (or shell) is curved, the pressure will vary between a kiln tire (tire) and the corresponding rollers during the kiln rotation, generating different crushing on every generatrix.
A
Beginning from "O" point the three lines OA, OB and OC are traced with 120º angles between them. Then for every tire or roller can be calculated the following:
tU + tJ taken from the Form 9.1.
Now in the diagram are traced (for example in scale of 2 : 1), the values tA = Oa, tB = Ob and tC = Oc. A circle is traced by crossing the points a, b and c with its center in M. From Pole O a line is traced crossing M, cutting the circle in D.
A wire trial of lead wire performed in the generatrix D kiln, located at Vº from generatrix A in direction towards B, will mark the maximum crushing, i.e. equal to OD distance, measured in the diagram.
If the major mean width tD, divided by the minor one, generates as result a major value of 1.3 , then the kiln tube must be straightened.
If the lead wires crushing in a tire is higher in one roller than in another one, the reason is because the rollers have been laterally displaced. The pressure coming from the sprocket and the kiln load can generate an unequal crushing and therefore, the rollers position in the lateral sense must not be corrected until the moment when confirming, through a control optic leveling, the kiln shaft.
The maximum surface pressure between the washer and the kiln tire can result as big as with risk of
"pitting" or "punctures" generation, if the kiln tube is not straightened.
9.3.4.6 Tires laterally displaced
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O
been laterally displaced. The pressure coming from the sprocket and the kiln load can have by effect an unequal crushing and therefore, the rollers (or tires) position in the lateral sense must not be corrected until the moment when, through a control optic leveling, the kiln shaft is verified.
The mean values tH and tV are divided, the highest by the lowest, and in this surfaces pressures ratio the following values can be expected:
In the support where the transmission is: 1.05 - 1.2
In the other supports: 1.0 - 1.1
If a higher ratio is checked, a support control leveling must be verified (i.e. the kiln alignment) and make a correction.
9.3.4.7 Kiln tire (tire) displaced in the vertical sense
If the mean width tL in one of the supports differ essentially from the others, correction must be made in the distance between both tires of each set, i.e. correct the kiln tire position height.
9.3.5 Safety aspects
It is always dangerous to work close to a rotary kiln. As when performing the lead wire trials it is required to work close to it, appropriate clothing, safety goggles, safety shoes, gloves and safety shield must be utilized.
9.3.6 Condemning or permissible limits
The differences in the crushing width, it means the values tu-tj or tj-tu, respectively, depend, among other factors, upon the kiln tire width, and 5 % of it must not be exceeded.
The kiln tube warping provides the mean width variance of the lead wires crushed of a same tire. If the mean width vary more than 30 %, the warping character and extension must be examined differently, considering a kiln tube straightening. If the mean width of all the lead wires crushed of a washer exceed more than 10 % then the mean width of all the lead wires of the other tire corresponding to the same support (but 20 % in the gearings set), the kiln must be submitted to a control leveling.
But the trial by itself evidences, if the optic control is immediately required:
It is not possible to determine in advance an admissible variance of the mean superficial pressure from one support to another, but it is valid as a general rule that if the mean surface pressure of a support apparently is extraordinarily big - or small - regarding the superficial pressures on the other supports, the kiln must be submitted to a control leveling operation.
9.5 ATTACHMENTS AND FORMS UTILIZED